The tiger pistol shrimp (Alpheus bellulus) belongs to the Alpheidae family, known commonly as snapping shrimp.
The Alpheidae family is incredibly diverse with over 500 unique species across the world. Alpheus bellulus shares a translocation and inversion event of trnE in its mitogenome with several other Alpheus species but there is not enough evidence to say this is a shared commonality among the entire genus. Phylogeny suggests Alpheus randalli and Alpheus bellulus belong to the same taxon within a monophyletic group. Amino acid composition of the cytochrome b protein in A. bellulus was also similar to those of A.randali and A. lobidens, two other species of snapping shrimp.
Description
The tiger pistol shrimp can grow to a size of up to , not including antennae. The body is stout and opaque. The background color of the body is yellowish white or plain yellow. The patterns drawn on the cephalothorax, abdomen and tail are irregular but symmetric; their coloration varies from light brown, brownish purple to brownish orange. The legs are banded with the same colors as the body and are covered with short bristles. The antennae are red. The chelipeds are also banded, with the right being bigger and modified into a powerful weapon. By closing at extreme speed, the cheliped expels an air bubble at more than towards the prey. This action is accompanied by a loud bang.
Alpheus bellulus use their oversized claws to produce powerful bubbles of air that stun its prey. Pressure builds up when the claw opens, and water enters a small chamber in the claw's bend. The claw quickly clamps down and a small plunger pushes water out with high pressure, releasing a high-speed bubble. This powerful sonic weapon creates a violent shock wave which can kill or knock out prey, which could be another shrimp or a small fish passing close to the tiger pistol shrimp.
The sound emitted from the collapsing bubble can be up to 218 decibels, with a temperature of up to 4,800 degrees Celsius, slightly cooler than the surface of the Sun.
Distribution
The tiger pistol shrimp can be found in the tropical waters of the Indo-West Pacific area.
Habitat
The tiger pistol shrimp dwells in sandy, muddy and detrital substrata in shallow waters up to .
The structure of the burrows made by A. bellulus, studied through resin casting, shows the three-dimensional shape and provides insight into the construction habits of the species.
A.bellulus relies on burrows for shelter and protection. In the beginning stage of construction, there is rapid growth in the size and dimensions of the burrow. During this phase, A. bellulus shows no interest in feeding or resting, placing total priority on burrow formation. This characteristic is similar throughout many alpheid shrimp species. A. bellulus is highly vulnerable to predation without a burrow, especially during the initial stages of burrow development, due to its limited vision and dependence on tactile cues from partner gobiid fish.
Burrows are reinforced with small pieces of shell and coral along the sides, preventing collapse. Sediment is constantly removed by A. bellulus to keep the internal burrow clean of settled deposits. Burrow production is also crucial to sediment cycling throughout the marine ecosystem, combining nutrients and debris along the seafloor.
Behaviour
Tiger pistol shrimp and gobies
The tiger pistol shrimp lives in burrows in symbiosis with certain goby species such as Cryptocentrus cinctus, Amblyeleotris guttata and Stonogobiops yasha. The shrimp digs and maintains the burrows used as dens by both animals, while the goby acts as a lookout and warns of danger the shrimp cannot easily detect because of its poor eyesight.
A study of goby fish and tiger pistol shrimp kept together in a tank found that when no other food source was available, the shrimp survived by eating the feces of the goby fish from within the burrow. This behaviour provides another example of the close partnership between the two species.
Goby symbiosis in Alpheus bellulus
The symbiotic relationship between the snapping shrimp Alpheus bellulus, typically found off the coast of Japan, and the gobiid fish Amblyeleotris japonica begins early in development and often continues into adulthood.
A. bellulus is not found in areas where the partner fish is absent and usually does not leave the burrow unless the fish is near the entrance. The shrimp stays in contact with the gobiid fish through its antennae and retreats into the burrow after noticeable movement from the fish.
In aquaria
The tiger pistol shrimp is one of the most popular pistol shrimp in the marine aquarium hobby as it has a peaceful temperament, is inexpensive and does not require complicated care.
Original publication
Miya, Y. & S. Miyake, 1969. Description of Alpheus bellulus sp. nov. associated with gobies from Japan (Crustacea, Decapoda, Alpheidae).— Publications from the Seto Marine Biological Laboratory 16: 307–314.